Recently, for controlling energy consumption of a consumer who receives power supply, power supplied to a facility of the consumer has been managed by providing a storage battery in the facility. For example, a storage battery and a solar cell are provided in the facility of the consumer, and a power conditioner controls power supply from an electrical grid to the facility, charging/discharging of the storage battery, and supplying or selling of power generated by the solar cell to the facility. An electric power rate is constituted by, for example, a basic rate of power and an amount-of-electric-power rate (pay-per-use) which is determined in accordance with power usage. The basic rate of power is set in accordance with highest peak power of power consumed by the consumer in the past. Thus, a threshold is set so that a level of power consumed by the consumer is not higher than a certain level, and power stored in the storage battery is supplied to the facility in accordance with a comparison result obtained by comparing an amount of the power consumed by the consumer to the threshold, so that it is possible to level the peak demand of the power consumed by the consumer. As a result, it is possible for the consumer to achieve reduction of the electric power rate while suppressing consumption of the power supplied from the electrical grid. In addition, also for an electric power supplier (electric power company) having a power station or a substation, there is an advantage in that power supply is stabilized by leveling loads, for example.
As a technique of achieving reduction (peak cutting) in a level of maximum peak power, for example, Japanese Unexamined Patent Application No. 2008-306832 (PTL 1) describes a power storage system that is able to reliably perform peak cutting while suppressing a capacity of a storage device. According to the technique of PTL 1, the power storage system performs switching between causing a secondary battery to charge in a night-time power time zone and causing the secondary battery to discharge in a daytime power peak time zone. Furthermore, in a case of a state where the storage device does not need to discharge and the storage device has not fully charged in the peak time zone, the power storage system causes the storage device to perform a charging operation. As described above, according to the description of PTL 1, the charging operation is performed when there is a margin in power demand in the peak time zone and the storage device has not fully charged, so that the storage device is able to keep a state close to the fully charged sate as much as possible.